The invention is directed to digital color printers, and methods of forming images on photosensitive media and the like. More particularly, the invention is directed to a system and method of forming multiple pixel images simultaneously via many concurrently operating beams of light.
Digital color printers, also known as imaging systems, form visually observable images on hard copy from electronic information. Examples include xerographic printers, ink jet printers, laser, LED and CRT imagers (including black and white or color, and imaging onto silver halide media), dye sublimation and wax transfer imagers, among others. With each type of system there is generally a computer file of electronic information which contains representations of photographic images, artwork, graphics and/or text, and there is a desire to obtain a paper or film hard copy from that data.
Electronic production and manipulation of images and text is highly efficient. It is becoming increasingly more common to store photographs as computer files rather than, or in addition to, pieces of film. The digital environment permits easy retouching and editing, addition of text and imposition of various photos into a layout. Moreover, in the case of color photographs, digital color lookup tables can compensate for deficiencies in the photographic media and in the exposure conditions. The existence of images in digital form creates a need for high quality imaging systems to create hard copies of these digital images.
Some imaging technologies require the use of light for the creation of a latent image on a xerographic drum or on silver halide media. One common way of doing this is to deflect a laser beam with a rotating polygon mirror. For exposure of color silver halide media, for example, three lasers are used, one each of (typically) red, green, and blue.
A commonly sought objective is to obtain high imaging speed, for example more than two square feet per minute; high resolution, for example more than 400 continuous tone pixels/inch (more than about 160 pixels/cm); and large image size, for example images from rolls of paper of 20" (approx. 50 cm) or greater width. It is also desired to minimize the size of the equipment used to produce this image. However, speed, resolution, image size, and equipment size tend to be competing factors that must be balanced or compromised.
One particular application for imaging technologies is in point of sale advertisements or trade show displays, many of which may need to be as large as 50".times.100" (approximately 125 cm.times.250 cm) or larger. In such cases, it is desired that the text be sharp, even at close viewing distances. It is also desired that the image be created in a short time, for example less than 10 minutes. These simultaneous objectives cannot be met or approached by conventional technologies.
Another application is the "package printer" market which requires that photos, such as school portraits, be imaged at various sizes and with the addition of text and other graphics. To compete with other processes the imaging speed must be at least 0.25 lineal inch per second (approximately 0.6 cm per second), and text even as small as 4 point size must be clearly readable. Again, this is not currently possible with conventional technologies.
Another application is the pre-press market, wherein proofs of information are desired in advance of the direct imaging of printing plates. The proofs should show true colors, should show the halftone dots, and they should be imaged quickly, in a few minutes or less. This is not possible with conventional technologies.
Many other applications exist for a digital color printer. Digital cameras are becoming available which bypass the use of film, but allow no alternative but that the hard copy be produced by a digital rather than film-based device.
Therefore, a substantial need has arisen for an imaging system offering high speed, high quality color, high resolution, large image size, small equipment size, and moderate equipment cost. This is not possible with ink jet technology, 3-laser technology, CRT technology, xerographic technologies, LED technology, or other known conventional technologies.